If you have already purchased a Plan with a set number of files, you can add and pay for additional files only when you need them.
If you start to create a new file, but you don't have any 'spare', you will be able to create the file, but you will be charged a prorated rate for that file for the month you are in.
Once payment has been received, your additional files will be made available in your account.
After your initial prorated invoice, you will commence paying the new additional file fees on your next monthly renewal.